Category: Tips

Let’s Learn About The htop System Monitor

There are any number of tools out there to monitor your system and today we’ll cover the ‘htop’ system monitor. This htop application is a pretty solid application and one that you might want to be familiar with. So, let’s learn about htop…

First, your Linux desktop comes with a system monitor called ‘top‘. This is true for so many distros that we might as well accept it as fact. The top application has been around 40 years at the time of this writing and it stands for ‘Table Of Processes’.

The top application is a task manager and system monitor, allowing you to manage processes while also monitoring system resources. You can learn a lot from top, such as uptime, RAM use, CPU use, the number of running processes, and so much more…

top:

If you want,  you can open top with the following command:

(You can just press Q to exit top.)

The output should look a little like this:

An example of top running in the terminal.
This is the top application, which you may already be familiar with…

The man page describes the top application as:

top – display Linux processes

The man page for the top command will also explain that you can do the following with it, which you may find interesting.

As you can see, top is pretty versatile. 

So then, what is htop?

htop:

The name is htop simply because the author’s name is Hisham. It is otherwise similar to the top application but comes with some great benefits. Another great benefit is that htop is going to almost certainly be available for your distro. Some distros have started installing htop by default.

Why htop instead of top?

Well, for starters the layout is much nicer. You can also use your mouse to control htop. This includes scrolling, making it easy to navigate. You can kill processes like this, change their nice value, and more. Additionally, you can even kill multiple processes at the same time.

You can filter and search easily with htop, meaning you can narrow down the results and keep it easier to read. On top of that, htop has a cascading tree layout for the processes. 

I’m told that htop is quicker due in part to how it gathers the information but I have no way to verify this. Both applications seem reasonably quick to me, but that’s what they tell me. I believe this has something to do with being ncurses-based. 

You’ll also click the setup option and configure htop to your needs. It has a nice colorful layout that is quite intuitive. Filtering is also easy, as is searching. Those both come in handy when you want to kill some processes all at once.

If you’re curious, htop looks like this:

running htop in the Linux terminal
It’s more colorful and easier to navigate with a mouse – but you don’t need a mouse to control it.

There are times when you can’t access your GUI system monitor to clear out frozen processes or things like that. So, you should get used to either top or htop. I think you’ll find htop is more featureful and useful in modern times. Even if you can’t use a mouse at the time (say you’re in a TTY), htop is still easy to operate, which is nice.

Install htop:

As I mentioned above, some distros (like Ubuntu) now include htop by default. There are older versions of Ubuntu out there that are still supported, so I’ll include htop installation instructions for them. Then again, they’d be the same instructions used by Debian, so it wouldn’t be that hard to figure out.

For simplicity’s sake, let’s install htop with the terminal. That’s a fairly universal thing. Most of the time, you can open your terminal by pressing CTRL + ALT + T. Otherwise, you’ll find a terminal option in your application menu.

With your terminal open, use the correct command for your package manager:

Debian/Ubuntu/etc:

SUSE/OpenSUSE/etc:

Fedora/etc:

Rocky/Alma/etc:

Arch/Manjaro/etc:

One of those should work for you.

The syntax to use htop is just this:

There aren’t a bunch of flags to worry about, but it’s worth checking the man page:

If you’re going to learn anything from the man page, you might want to learn the keyboard shortcuts for when you do need to use htop without a mouse. There are many, but learning the basics will take you ten minutes. I’d call that ten minutes that were properly invested because htop is a great application.

There you have it.

You should now have htop installed and know how to run the application. I think you’ll like it more than you liked top. I know I do. It’s definitely what I prefer of the two – but it’s not the only option.

Closure:

I’ve wanted to write this article for a while but just didn’t want the hassle of writing it. I finally had both time and motivation, so I wrote the article. There’s some chance that a major storm is going to take out my internet, so I might as well leave you with a good article to keep you going. Now you know about htop, a top replacement. That’s a good thing.

Seriously, I prefer htop over top. It’s just much nicer and easier to work with. Be sure to check the setup options because you can configure htop to your liking. That’s a handy feature to have.

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Mastering The Power Of Linux Tee Command

I want to write an article that includes the Tee Command but it was one of those commands that I didn’t seem to be able to write properly. I wrote this article manually before I realized how much I was not too fond of the outcome.

So, I decided to lean on AI again. This seems like a fine article for AI to write, so let’s see how it did. (Hint: It did much better than I did…) I think I’m learning how to use AI as a tool to help me. That’s a good role for AI and is one of the reasons I’m not too worried about our future.

Mastering The Power Of Linux Tee:

In the vast landscape of Linux commands, few hold the versatility and power quite like tee. Often underestimated, the tee command is a true powerhouse for those who dare to delve deeper into its capabilities. If you’re ready to elevate your Linux command line skills, then it’s time to master the art of tee.

Understanding the Basics:

At its core, tee is a simple yet elegant command designed to read from standard input and write to both standard output and files simultaneously. Its syntax is straightforward:

This means you can use tee to capture command output and redirect it to multiple destinations, whether it be a file, a pipeline, or even another command.

The Power of Redirection:

One of the key strengths of tee lies in its ability to redirect output to multiple files. This comes in handy when you need to save the output of a command for later analysis while still seeing it in real time. For example:

This command will display the output of ls -l on the terminal and simultaneously save it to both file1.txt and file2.txt.

Piping Output for Further Processing:

Tee can also be combined with other commands using pipes to create powerful data processing pipelines. For instance:

In this example, the output of cat file.txt is simultaneously filtered by grep to find lines matching a certain pattern and those that don’t. The results are then written to different files.

Appending to Files:

While tee typically overwrites the content of files, it also supports the -a option to append to existing files. This can be useful when you want to continuously add data to a log file without losing previous entries. For instance:

This command will append “New entry” to logfile.txt without deleting its existing content.

Real-World Applications:

The versatility of tee makes it indispensable in various real-world scenarios. Here are a few examples:

Monitoring System Logs:

This command continuously monitors the system log (syslog), saves a backup copy to syslog_backup.txt, and filters out lines containing the word “error” to create a separate error log.

Debugging Scripts:

When debugging a script (script.sh), redirecting both standard output and standard error to a file using tee allows you to analyze any errors or unexpected output more effectively.

Capturing Command Output:

In the realm of Linux command-line utilities, tee stands out as a versatile and powerful tool. Whether you’re redirecting output to multiple files, creating complex data processing pipelines, or simply monitoring system logs, tee proves to be an invaluable ally. By mastering the art of, you unlock new possibilities for efficient data manipulation and analysis on the Linux command line. So, next time you need to capture command output or create intricate data workflows, remember the power of tee and wield it with confidence.

Closure:

Yeah, that sums up the tee command. AI really can do a better job than I can do with certain subjects. I wish I’d had this tool available for some of my more basic articles. AI would do a better job than I, as it certainly did with the tee command. I did have to edit this one quite a bit, but it’s an acceptable article. I might do more with AI but I did want to cover the tee command.

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How To: Remove A PDF Password

This will be a straightforward task for anyone who would like to know how to remove a PDF password in the Linux terminal. If you deal with a lot of PDFs and want to remove the password, it’s a fairly easy task. Read this to learn more!

As mentioned before, PDF stands for Portable Document Format. This is a ratified ISO standard (ISO 32000) and is an open standard. You can see a bit about the PDF standard here on the ISO website. However, unless you have a subscription, they’ll want you to pay for this. I am not paying for this as I do not need to know the specifics.

Many people think that it’s proprietary because it comes from Adobe, but it’s an open standard and there’s a bunch of software available to manipulate and create PDF files. The standard has been open since 2008 which explains the myriad choices for editors.

Seeing as you’re here, you might as well read this interesting Wikipedia article:

History of PDF

PDFs can come with different levels of security. They can have passwords that lock the ability to edit the file and they can have passwords that you need just to open the PDF file.

This article assumes that you know the password! The exercise in this article only applies if you already know the password. I did write an article about cracking a PDF password, but that can take a long time.

How To: Crack A PDF Password

So then, which tools are we going to use?

poppler:

We’ll be installing a meta package known as poppler. This may come pre-installed on your system, or you may need to install poppler manually. We’ll go over installation instructions for a variety of distros, as it’s widely packaged and available in the various distro’s default repositories.

You’ll find that poppler is a meta package. That is, it contains other packages. In this case, poppler contains other applications that are used to manipulate PDF files. There’s no such thing as man poppler for example. It’s just the package name for a package that contains other packages. (That’s a meta-package.)

If you dig into it, you’ll find that poppler contains applications like pdffonts and pdfimages. At this point, we’ve previously covered pdftotext. This time around, we’ll be using pdftops. We’ve not yet used this tool in other articles, so now is as good a time as any to learn about it.

pdftops:

This pdftop application is mostly intended to turn PDF files into PS (PostScript) files but has other uses. Sort of like how a medication can be prescribed off-label, so too can you use this tool for other things. This time around, we’ll be using the pdftops to remove a PDF password.

If you had poppler installed already and checked the man page, you’d see something that should be close to this:

pdftops – Portable Document Format (PDF) to PostScript converter (version 3.03)

We’ll be skipping that whole bit about converting it to a file formatted for PostScript. That’s not necessary for our goal – removing a password from a PDF-formatted document.

But, this tool contains the necessary commands to remove a PDF password. If the file has multiple passwords it will remove the password specified. Your best bet is to remove the password that enables editing. This will also unlock the PDF for viewing purposes.

Remove A PDF Password:

If you want to remove a PDF password, you can use a GUI tool and then choose the ‘export’ option – or maybe the ‘save as’ option. In our case, and as mentioned above, we’ll be using the terminal to remove a PDF password. If you don’t know how to open a terminal, that’s usually accomplished by finding the application in your menu or by pressing CTRL + ALT + T on your keyboard.

With your terminal now open, we need to install the poppler meta package. I’ll include the commands as I understand them but you may need to doublecheck my work. Depending on your package manager, try the following:

Debian/Ubuntu/etc:

RHEL/CentOS/etc:

OpenSUSE/SUSE/etc:

Gentoo:

Arch/Manjaro/etc:

One of those should work with all the major distros out there. If you’re using an obscure distro with an obscure package manager, the poppler utilities should be available to you. You’ll just need to edit your installation command to match your package manager.

Also, if you do need to do that, please let me know. If you let me know, I can include the command in the article, thereby making the article more useful to more people. One of my primary goals is to be useful. It’s good to be useful to more people.

On to the meat of the article:

Removing A PDF Password:

As you’ve already got your terminal open, you might as well keep that terminal open. The application we’re using is pdftops and you can use the following command to ensure that pdftops is properly installed:

The output should look similar to this:

While you’re there, you can check the man page. There are many options available for the pdftops command and you can check them with this command:

Now that we’ve checked the man page, we’re looking for the -upw flag. That’s the flag that’s going to do the heavy lifting and the man page describes it like so:

Specify the user password for the PDF file.

So, you can see where this is going…

The syntax is quite simple. It will look like this:

If you want to specify the owner password, you use the -opw flag. You can pick which password it is that you’re using and the output file will not have that password. Specifying this flag will remove all restrictions, of course.

Let’s try to give you an example…

I wrote an article about how to crack a PDF password and I included a link. For the sake of clarity, you can now download that PDF file.

Example PDF File

The password for that file is ‘abab’ and not one of you took the time to crack it. I made it nice and simple for you, but not one of you took the time to crack the password.

Still, we can use that in our example:

Rather than converting to PostScript, we are just opening and unlocking the file. At that point, we’re redirecting that unlocked content to a new PDF file. In the process, we’re stripping the existing password, meaning you can easily access the file in the future – even if you’ve long since forgotten the password.

Closure:

I’m not sure how often you work with PDF files, but this might be something you can use. You don’t need to remember complex passwords unless you want to. Very few people are interested in maintaining a mental list of all the passwords they use.

It’s not like there’s a password manager for PDF files (as far as I know). You’re stuck referencing the original place the password was shared or keeping some sort of list. Well, you do have another choice. You can learn how to remove a PDF password in the Linux terminal and be done with it. It’s up to you.

Anyhow, I figured this would make a good article. I don’t mention PDFs often and don’t write many articles on the PDF subject. There have been a few of them but there’s always more to cover. Today we just covered how to remove a PDF password. Maybe we’ll cover something else in the next article – but I’m more likely to skip a few articles so that it’s not just PDF content for a week.

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Another Way To View Attached Storage Devices

Linux offers myriad ways to accomplish the same task, which is a good thing, and this is another way to view attached storage devices. This is a useful way to learn more about your storage devices and is a bit more advanced than others.

There are many ways to view attached storage devices. While not the same, you can learn which storage devices are attached to your system with any of the following articles:

Show Your Filesystem In The Linux Terminal
Show Mounted Partitions
How To: List Mounted Partitions
Yet Another Way To Check Filesystem Space Use

Stuff like that…

Well, you can also just plain old view attached storage devices in the Linux terminal. The application I’ll be showing you will do more than this, but we’ll concentrate on just showing attached storage devices.

The tool we’ll be using is known as:

lsscsi:

Yes, we’ll be making use of the lsscsi application for this article. This won’t take very long and you should find that lsscsi is available for pretty much every operating system out there. It does what you’d think, list SCSI devices.

Once installed, you could check the man page to see that this is the correct tool if your goal is to view attached storage devices. The man page describes the lsscsi application like this:

lsscsi – list SCSI devices (or hosts), list NVMe devices

It’s a simple application, at least for our needs. You’ll find that you can get some of the same information with the following command:

However, that command won’t give you things like the path. Mounted storage devices tend to have a path of something like /dev/<path>, and that information isn’t available with the cat command listed above. As we often want to know the path information, and there are many tools to do this, you might as well learn about lsscsi. 

By the way, your GUI disk manager (such as gnome-disks) will happily give you some of this information. It’s also a graphical environment, which may be easier for some folks. This is for those needing that information while using the terminal, or for those who are just interested in doing more in the terminal.

But, when it comes to disk and data management, you may need to know this information – especially the paths. So, this is a good command to have in your pocket. You never know when it will come in handy.

View Attached Storage Devices:

If you’re unfamiliar with the lsscsi application, it’s a terminal-based application. If you’re already familiar with the lsscsi application, I’m not sure why you’re still reading the article! Either way now is the time when you open a terminal. Oftentimes, you can open a terminal by just using your keyboard. Try pressing CTRL + ALT + T and your default terminal should open.

With your terminal now open, it’s time to install lsscsi. The directions to do so will depend on your package manager, but I’m going to cover most of them because this application is widely available and packaged for almost anything you can think of.

Installing lsscsi:

With your terminal open, use the correct command for your package manager:

Debian/Ubuntu/etc:

RHEL/CentOS/etc:

Gentoo:

OpenSUSE/SUSE/etc:

Arch/Manjaro/etc:

One of those should work for most of you. If not, let me know in the comments and I’ll amend the application. If they’re wrong, please do let me know in the comments. I did not test all of these. I’m going with a combination of my notes and what I’m able to scrape from the internet.

Using lsscsi:

With that open terminal, just enter the name of the command and you have about all the use you’ll really need from the application. The command is simply:

If you want, there’s more to the application – which you might need for some advanced operations. You can just check the man page with this command:

Here’s an example output:

Here’s another example output:

If you look at the bottom one, there’s a bit of an Easter Egg. You’ll see that it starts with an N and that means it’s an NVMe device. You don’t need any special tools beyond lsscsi to view NVMe devices, which is nice. The program happily recognizes it and other attached storage devices.

Closure:

You never know when you’re going to want to view attached storage devices. However, the odds are good that you’ll eventually want to know this information. It’s always good to verify the path of a dd command, for example. A malformed command can really cause you some problems.

So, now you know how to view attached storage devices – a task that has many solutions in Linux. There’s nothing wrong with variety and each of the various tools will have different strengths. Knowing what to use and when to use it is something you’ll learn as you make progress.

Thanks for reading! If you want to help, or if the site has helped you, you can donate, register to help, write an article, or buy inexpensive hosting to start your site. If you scroll down, you can sign up for the newsletter, vote for the article, and comment.

Turn PDF Into Text

Today’s exercise is simple, though it will rely on the terminal because we’re just going to turn PDF into text. This isn’t something complicated and it’s fairly effective. It’s also an exercise anyone can follow along with. So, if you want to turn PDF into text, read this article!

I’m sure this works in multiple distros, but I only have instructions for a few in my notes. Most everyone should be able to follow along with this article and turn PDF into text. You’ll see…

While I’m sure everyone is familiar with PDF, I’ll explain…

PDF stands for Portable Document Format and is one of many standards for documents. Specifically, it’s ISO 32000 and is a file format brought to use by Adobe. Adobe is a proprietary product but the standard is open, meaning you have your choice of PDF readers, editors, and creators.

On the other hand, PDF may not be as easily parsed as other file formats. You may also just want to extract some text from a PDF or turn it into something more information-dense, sans pictures and fluffy formatting. There are any number of reasons why you might want to turn PDF to text and it’s a simple operation that’s going to give you ‘acceptable’ results most of the time.

The tool we’ll be using…

pdftotext:

We’ll use a tool known as ‘pdftotext’ which does as its name implies. It’s a tool that lets you turn PDF into text, so from .pdf to .txt is the goal. Like many Linux tools, this is a terminal-based operation.

You can check to see if pdftotext is already installed with this command:

If the output matches this, you can skip the installation step:

If you want, you can check the man page and see that it is indeed the correct tool for the job if your job is to turn PDF into text. That’s this command:

That command will show you that the description is indeed what we want to accomplish in today’s article. That description is basically:

pdftotext – Portable Document Format (PDF) to text converter

(It may also tell you the version in that section, which is odd but is what it is.)

So, you can see that pdftotext is the correct tool for the job when you want to…

Turn PDF Into Text:

As I mentioned in the intro, if you want to turn PDF into text one of the ways to do so will require using the terminal. There are all sorts of GUI tools you can use to do this very same job, but we’ll do this in the terminal. So, you can usually get away with pressing CTRL + ALT + T to open your default terminal emulator. Otherwise, check your application menu and you’ll find a terminal option in there.

With your terminal open, we first will install a meta package so that we can use pdftotext to turn PDF into text. That application is ‘poppler’. You can pick from the following to match your package manager to install this.

Debian/Ubuntu/etc:

Arch/Manjaro/etc:

RHEL/Fedora/etc:

The poppler package contains pdftotext which is the tool we’re after in our quest to turn PDF into text. It’s a noble quest!

Now, the syntax is quite simple:

That will create a <file_name>.txt file in the same directory.

Now, if you checked the man page above, you’d see that there’s not a whole lot to this application. You can largely ignore all the options (and we will), though there aren’t that many.

The two options we are most interested in would be about just converting single pages into text. For that, you want the -f (first page) and -l last page flags. They do exactly what you’d expect and the syntax is as follows:

I’ll give you an example…

Let’s say you want to print pages 1 through 3. The syntax would be:

Sometimes this whole pdftotext thing doesn’t do a great job. If the PDF file is formatted in a fancy manner, it may just not come out in text all that well. Fortunately, PDF is an open standard and you can help it along with the -layout flag. 

The -layout flag is described like this:

Maintain (as best as possible) the original physical layout of the text. The default is to ´undo’ physical layout (columns, hyphenation, etc.) and output the text in reading order.

So, that flag will do its best to turn the layout into what it was in the original PDF. This is a handy flag for when the output isn’t usable. It’s possible to retain columns, advanced formatting, and all of that stuff, meaning the text file output is more useful. You won’t always need this option, but it can come in handy. You can safely ignore the remainder of the man page for the vast majority of what folks are going to do with this command.

That’s pretty much all you need to know about the pdftotext application. It does what you think it’d do. It’s the tool you use to turn PDF into text, just like it says on the tin! Pretty handy!

Closure:

So, that’s an article… 

If you’ve ever wanted to turn PDF into text, you now know how. You can use this to make a PDF easier to parse, easier to read, etc. It’s up to you how you use pdftotext. You now have the knowledge! You now have the power! Indeed, you have life by the horns. (Which is a rather silly place to grab onto.)

Man, this is a lot of articles… At this point, it’s almost habitual. Technically, I have published something every other day – for a long time. A couple of those articles weren’t really articles. They were placeholders because Mother Nature is a fickle beast and I live in a very remote location. We had a few major (deadly even) storms that took out our infrastructure. I think I can be forgiven for that – and I did upload articles saying that there’d be no article. 

The site has come a long way…

I haven’t done a meta article in a while…

Seriously, without you (my readers) I’d have never kept going this long. It’s obviously not a money-making operation, but it is an educational operation. That’s more important than money.

Thanks for reading! If you want to help, or if the site has helped you, you can donate, register to help, write an article, or buy inexpensive hosting to start your site. If you scroll down, you can sign up for the newsletter, vote for the article, and comment.

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